To prevent quality defects due to equipment or process conditions, we have to establish the conditions under which the equipment or process will not produce any defects. To do this, we must fully co-ordinate our quality assurance activities and equipment management activities, and identify how the product’s quality characteristics are affected by materials, methods and equipment precision.
Establishing zero-defect conditions involves identifying the exact group of causes behind any possible defects, and then setting ranges for the material conditions, method conditions and equipment precision, so as to ensure 100% good product. The central philosophy of Quality Maintenance is to sustain and control the established conditions, and consequently achieve zero defects, and this approach relies on having operators who are fully conversant with their equipment and have been trained in Autonomous Maintenance and other relevant skills (see Figure “The Basic Approach to Quality Maintenance”).
Achieving perfect quality requires an important shift in attitude – from the conventional approach, where defects are only discovered when the product is inspected, and action is taken after the event, to an approach in which each condition affecting quality is measured periodically, and preventive action is taken before that condition exceeds its permitted range.
This chapter looks at how to establish, standardize and improve zero-defect conditions for materials, machinery and methods.
The 4 Ms – the Determinants of Quality
The key to ensuring quality (i.e. production standards) on the shop floor is achieving optimal conditions for the 4 Ms (Men/Women, Machinery, Materials, Methods), see Table “The 4-M Conditions – The Determinants of Quality”.
Improving quality means establishing optimal conditions for the 4 Ms, raising the quality assurance capability (Cp) of the process until it stabilises at a high level, and setting work standards and inspection standards to maintain that capability. Sustaining quality, on the other hand, means faithfully applying the work standards and inspection standards that maintain the optimum conditions we have set. Figure “The 4-M Conditions – The Determinants of Quality” illustrates this relationship.